Optical fiber connectors and splices (hereinafter referred to collectively as "connectors") are an essential part of substantially any optical fiber communication system. For instance, connectors may be used to join segments of fiber into longer lengths, or to connect fiber to active devices such as radiation sources, detectors, or repeaters, or to passive devices such as switches or attenuators.
The task of an optical fiber connector is twofold. First, it must couple or join two optical fibers with minimum insertion loss. Second, it must provide mechanical stability and protection to the junction in its working environment. Achieving low insertion loss in coupling two fibers is generally a function of the alignment of the fiber ends, the width of the gap between the ends, and the optical surface condition of either or both ends. Stability and junction protection is generally a function of connector design, e.g., minimization of differential thermal expansion effects.
The prior art knows many approaches to achieving fiber alignment. Among them are V-grooves, three-rod containment, resilient ferrules, elastomeric bushings, jewel bushings, conical nose/conical bushing, and precision ferrule/precision bushing devices. A discussion of some prior art connectors can be found, for instance, in R. Schultz, Proceedings of the Optical Fiber Conference, Los Angeles, (September 1982), pp. 165-170.
For example, U.S. Pat. No. 4,205,897, issued June 3, 1980 to W. C. Stankos, for "Fiber Optic Connector for Single Fiber," discloses a connector and coupling assembly for coupling a single pair of optical fibers in which the respective fibers are secured in identical metallic connector pins inserted into an alignment sleeve having a precision axial aperture. As a further example, U.S. Pat. No. 4,135,781, issued Jan. 23, 1979, to J.D. Archer, for "Optical Fiber Termination", discloses a method for terminating an optical fiber by means of a connector by pushing the plastic-clad optical fiber into a heated ferrule containing a pierced watch bearing jewel, so as to force the bare fiber through the aperture in the jewel, then fusing the protruding fiber end, and polishing the fused fiber end flush with the jewel surface.
A further example of prior art connectors is described by R. Schultz (op. cit.). (See also Design News, Dec. 6, 1982, pp. 60-61.) The connector described therein comprises a glass tube, factory-bonded to a metallic connector body assembly. Stripped fiber is threaded through the bore of the glass tube, and held in place therein by means of UV-curable adhesive. A metal ferrule is slipped over the length of fiber jutting from the glass tube/body assembly and held in place by means of a coupling ring. The fiber end protruding from the slightly concave ferrule surface is scribed and broken close to the ferrule. The ferrule can then be inserted without further processing into a mating bushing of an appropriate adapter or receptacle to complete a connection.
Prior art optical fiber connectors typically contain one or more precision machined parts and are therefore relatively costly items. Whereas this may be acceptable for some applications, e.g., in trunk lines, in other cases the price of connectors of the prior art type might constitute a significant fraction of the total installation price. An example of such an installation is considered to be a local area network (LAN), which usually would require many, perhaps hundreds, of fiber connectors.
A further and very important consideration is the relative ease of field installation of an optical fiber connector, since a complicated and lengthy installation procedure may significantly affect the installed price of a multi-connector optical fiber network. It is thus desirable that the installation of a connector not only be accomplishable within a relatively short period of time but also that the installation not require special skills, or manipulations not easily carried out in the field.
It is thus evident that an optical fiber connector whose parts can be easily and inexpensively produced, which can be quickly and simply installed by relatively unskilled personnel in the field, and which, furthermore, is compatible with all environmental conditions it is likely to encounter, and which has extremely low insertion loss, would be of great commercial importance. This application discloses such an optical fiber connector.